Telephone-exchange system



R. S. WILBUR.

TELEPHONE EXCHANGE SYSTEM.-

APPLICATION FILED MAY 13, 1918.

1,324,364. Patented Dec. 9,1919.

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. RAY s. WILBUn, or nrnnnnns r, new JERSEY, assrenoa T0 wnsrnnnnrnc'rnro columns, INCGRPORATED, or new iron-inn. Y.,

A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

asagna;

Application filed May 13, 1918.

To all Mam it mayconcera:

Be it knownthat 1, Key S. VVILBUR, a

citizen of the United States, residing at Lyndhurst, in the county ofBergen, State of New J ersey, have invented certain new and usefulImprovements in Telephone-Exchange Systems, of which the following is afull, clear, concise, and exact description This invention relates totelephone exchange systems and more particularly to those in which trunkcircuits are employed in completing connections between telephoneswitchboards oroflices.

In such systems it is desirable to provide signaling means wherebytheoperators handling the connections are definitely advised as to theanswered or unaswered condition of the called telephone station.Especially operator controlled signaling means,it is very desirable thatthe completing or trunk operator receive an ac to provide an improvedsystem of this character which will be simple and inexpensive and willprovide a definite signaling means solely responsive to the answer ofthe called station and unaflected by changes in the electricalconditions ofthe trunk circuit incident to the establishment of thetelephonic connection.

To attain this object, in accordance with a feature otthe'invention, atrunlrcircuit provided with the usual ringing signal controlled by asupervisory relay and adapted to indicate when the called stationanswers, is associated with means to prevent'a pre mature indicationbeing given by the signaling device due to an incidental momentaryoperation of the supervisory relay prior to the response of thecalled-station.

The nature of this invention will more fully appear from the followingspecification and annexeddrawing in whichthe figure showsdiagrammatically a trunk circuit embodying the invention and suflicientportions of a line circuit and of a link circuit for cooperationtherewith, to properly illus- 50 trate, the operation of the system.

In the accompanying drawing, a trunk circuit D interconnects theswitchboards or offices B and C. terminating-at office B in a plug 5andat ofiice C in a jack 14. An ordinary line circuit A equipped with theusual Specification of Letters Patent.

.. in jack 1 of line operates,

Patented Dec. 9, 1919. Serial No. 234,346.

line relay 3, cutoff relay 2 and line signal 4 terminates in a jack 1 atotfieeB. A connecting or link circuit E of any usual type is provided atotlice C and terminates in a plug 15' for connection with jack 1% of thetrunk circuit Dr The portions of the link circuit (not shown), have beenomitted since they are unessential to a proper understanding of theinvention.

It is thought that. the invention may be more fully (oniprehended fromthe following description of the operation of the system.

Assuming that the operator at switchboard C desires to call station A onthe line terminating in ja k 1 at station E; the operator at B isnotified in some suitable manner over a call circuit or otherwise andassigns trunk circuit D. The operator at C thereupon inserts plug 15 ofthe link circuit E in the jack 14: of the trunk circuit D. The lamp 17is lighted over a circuit extending from battery through the lamp 17,the resistance 16 and the sleeve contacts of plug 15 and jack 14 toground. Relay 13 is also operated over acircuit extending from batterythrough the winding of relay 19, the ring contacts of plug 15 andjack14, the right-hand winding of relay 13. the tip con tacts of jack 14 andplug 15 to ground. However due to the high resistance of the right-handwinding ofrelay 13'. the superternate contact of relay 13 to ground. Be-

lay 8 is also operated over a circuit established from battery throughthe resistance 21,-the winding of relay 8 and the alternate contact ofrelay 13 to ground. The operator at switchboard B thereupon inserts plug5 A, completing a circuit extending from battery through the winding ofrelay 9, the sleeve contacts of plug 5 and jack 1 and the winding ofcutofl relay 2 to ground. The operation of relay 2 thereupon removes theline relay 3 and its associated line signal 4- from their normalassociation with the line circuit A. The relay 9 also establishing thecontinuity of the tip conductor of the trunk circuit, but due to theoperation of relay 13 and of relay 8 no further useful function isperformed thereby at this time.

The operator at switchboard B then actuates the ringing ey 10 in theusual manner, impressing signaling current upon the V conductors of theline A. to cause the operation of the usual signaling device at thecalled station. The ringing key released after the signal at the stationon the line A has been operated, the trunk circuit apparatus is then incondition to respond to the answer of the called station. Upon theanswer of the called station, the supervisory relay 6 is operated over acircuit extending from battery through the winding of relay 6, the lowernormal contact of ringing key 10, the ring conductors of plug 5 and jack1 through the apparatus at the called station, the tip conductors ofjack 1 and plug 5, the upper normal contact of ringing key 10, and theupper alternate contact of relay 9 to ground. In operating, relay 6completes a shunt circuit for relay 8 including the left-hand normalcontact of relay 7, the contact of relay 6, and the middle normalcontact of relay 7. Due to the presence of this shunt circuit, relay 8releases, thereby completing a circuit from battery through the loweralternate contact of relay 9, the winding of relay 7, the contact ofrelay 8, the contact of relay 6, the

middle normal contact of relay 7 and the alternate contact of relay 13to ground. Relay 7 thereupon operates and by the openin of itsright-hand normal contact extingulshes lamp 12. A locking circuit isalso established for relay 7 extending from battery through the loweralternate contact of relay 9, the winding and the right-hand al ternatecontact of relay 7, the alternate contact of relay 13 to ground; Throughthe closure of its middle and lefthand alternate contacts, relay 7 alsoplaces the left-hand winding of relay 13 in parallel with the right-handwinding thereof in the usual manner, thus reducing the resistance of thecircuit including the supervisory relay 19 of the link circuit E. Theconsequent operation of relay 19 establishes the usual shunt circuitthrough resistance 18, around the lamp 17, thereby causing theextinguishment of such lamp. The operator at switc 1- board 0 may nowconverse wlth the station A upon the actuation of the usual listeningkey 20. Upon the completion of the conversation, the operator atswitchboard Cremoves the plug 15 from the jack 14-, thereby restoringthe apparatus associated with the link circuit E to its normal conditionand releasing relay 13 to cause the display of the disconnect lamp 11 atthe switchboard B, over a circuit established from battery through themiddle alternate contact of relay 9, the lamp 11, and the normal contactof relay 13 to ground, ZUpon observing the 10 being lighted condition oflamp 11, the operator at switchboard B removes plug 5 from jack 1,thereby restoring all apparatus to normal condition.

During the signaling of the called station, the condenser 22 and theconductors of l the line become charged and upon the release of theringing key 10, a discharge may take place through the winding of relay6, causing the momentary operation of such relay. However, the relay 8is adapted to be unaffected by any incidental momentary establishment ofthe shunt circuit therearound and will release only upon a shunt circuitof considerable duration. Therefore, the circuit of relay 7 is notcompleted due to any incidental operation of the relay 6 caused by thedischarge of the capacitance of the line A and the ringing signal lamp12 is not prematurely extinguished thereby.

What is claimed is:

1. In a telephone exchange system, a line circuit having capacitance, astation associated therewith adapted to be called, a trunk circuit forconnection therewith, a supervisory relay for the trunk circuit adaptedto operate upon the answer of the called station when the trunk circuitis connected with the line circuit, a signal control relay, a relayclosing the circuit thereof upon its release, and means operative uponthe discharge of the capacitance over the trunk circuit to cause amomentary shortcircuiting of the winding of the lastinentioned relay,said relay being unaffected thereby.

2. In a telephone exchange system, a line circuit, a station associatedtherewith adapted to be called, a trunk circuit for connection with theline circuit, a supervisory relay for the trunk circuit adapted tooperate upon the response of the called station, a signal control relay,a slow-release relay energized prior to the response of a called stationadapted to complete an energizing circuit for the signal control relaywhen released, and means efiective upon any incidental prematureoperation of the supervisory relay to establish a temporary shortcircuit around lease relay of insufficient duration to effect therelease thereof,

3. In a telephone exchange system, a line circuit, a station associatedtherewith adapted to be called, a trunk circuit for connec" tion withthe line circuit, a relay operating upon the connection of the trunkcircuit with the line circuit, another relay operating prior to theresponse of the called station, a supervisory relay operating upon theresponse of the called station to release the second mentioned relay bycompleting a short circuit therearound, and a signal control relayjointly pentrplled by the above mentioned r y 4:. In a telephoneexchange system, a line circuit, a station associated therewith adaptedto be called, a trunk circuit for connection with theline circuit, arelay operating prior to the response of the called station, asupervisory relay responsive to the answer of the called station toestablish a shunt around and thereby release the first mentioned relay,a signal control relay operating upon the release of the first mentionedrelay, and a'locking circuit for the signal control relay completed uponthe operation thereof.

5, In a telephone exchange system, a line circuit, a station associatedtherewith adapted to be called, a trunk circuit for connection with theline circuit, a first relay operating upon the connection of the trunkcircuit with the line circuit, a second relay operating independently ofthe connection of the trunk circuit with the line circuit, a signalcontrol relay, an energizing circuit therefor completed upon thecontemporaneous energization of the first relay and the release circuit,a signal control relay operating upon the contemporaneous operation ofthe sleeve relay and the release of the slow-release relay, and asupervisory relay responsive to the answer of called station toestablish a short circuit around the slow-release relay of suflicientduration to cause its release.

' In witness whereof, I hereunto subscribe my name this 9th day of May,A. D;, 1918.

RAY s. WILBUR.

